Drag coefficient shows non-realistic values

hotti24 · December 12, 2022, 04:18

Good Morning CFD Engineers!

We did a simulation of a C-shaped geometry (1.5m height x 4 m length) which faces an airstream with the open side of approx. 15 m/s.

In various CFD-Simulations we always got a drag coefficient of approx. 0.8 while Wikipedia-tables shows 2.3 for open half pipe. Client points out, that the 2.3 is realistic from experimental experience.

We did not see changes with different turbulence models or LES Simulation. There was only one simulation where we increase k significantly in the k-epsilon model. In this simulation we got a value of 1.2.

Does anyone have an Iidea what we have to change to reach higher values?

Cheers!

wkernkamp · January 14, 2023, 00:20

I would suspect your domain is not big enough or it has the wrong boundary conditions.

December 12, 2022, 04:18	Drag coefficient shows non-realistic values	#1
hotti24 New Member Hendrik Join Date: Jul 2013 Location: Germany Posts: 9 Rep Power: 13	Good Morning CFD Engineers! We did a simulation of a C-shaped geometry (1.5m height x 4 m length) which faces an airstream with the open side of approx. 15 m/s. In various CFD-Simulations we always got a drag coefficient of approx. 0.8 while Wikipedia-tables shows 2.3 for open half pipe. Client points out, that the 2.3 is realistic from experimental experience. We did not see changes with different turbulence models or LES Simulation. There was only one simulation where we increase k significantly in the k-epsilon model. In this simulation we got a value of 1.2. Does anyone have an Iidea what we have to change to reach higher values? Cheers!

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January 14, 2023, 00:20		#2
wkernkamp Senior Member Will Kernkamp Join Date: Jun 2014 Posts: 372 Rep Power: 14	I would suspect your domain is not big enough or it has the wrong boundary conditions.